ne plus ultra

From Latin, literally, not further beyond. Earliest documented use: 1637.

NOTES:

It's said that the Pillars of Hercules at the entrance to the
Strait of Gibraltar had this Latin phrase inscribed. It served as
a warning to sailors not to go beyond the limit of the known world.
The national motto of Spain, on the other hand, is "Plus ultra".

USAGE:

"The greatest car in the world, the automotive ne plus ultra."
Jonathan Carroll; The Ghost in Love; Farrar, Straus and Giroux; 2008.